1. Field of the Invention
The present invention relates to an insulating substrate, a method of manufacturing the same, and a semiconductor device.
2. Description of Related Art
As a semiconductor device that includes a semiconductor element mounted on an insulating substrate, a semiconductor device that is installed in a vehicle and has a function of power control and the like has been known, for example.
In such a semiconductor device, generally, there is a possibility that a joint portion of soldering or the like that is interposed between the semiconductor element and the insulating substrate or a metal layer (wiring pattern) that is provided in the insulating substrate is peeled or cracked due to a difference in coefficients of linear expansion among materials used for the semiconductor element and the insulating substrate.
A stress caused by the difference in the coefficient of linear expansion is mainly generated at four corners of each component that constitutes the semiconductor device as starting points. Accordingly, the metal layer that is provided in the insulating substrate may be peeled or cracked mainly from four corners toward the center. When peeling or cracking occurs, a portion of the insulating substrate that is peeled or cracked increases thermal resistance, and a heat radiating property of the semiconductor element declines. Therefore, it has been suggested to detect occurrence of peeling or cracking in the insulating substrate based on transitions of temperature or resistance, for example.
However, the occurrence of peeling or cracking cannot be detected directly by a detection method based on the transitions of temperature or resistance but is detected indirectly. Thus, due to the influence of noise or the like, it is difficult to accurately detect the occurrence of peeling or cracking. In other words, it is difficult to identify a portion that is peeled or cracked. In addition, a complex mechanism has to be provided exclusively to manage the temperature or the resistance.